Feedforward correction of mirror misalignment fluctuations for the GEO 600 gravitational wave detector

Smith, J. R.; Grote, H.; Hewitson, M.; Hild, S.; Lück, H.; Parsons, M. L.; Strain, K. A.; Willke, B.

doi:10.1088/0264-9381/22/14/018

Cited by 3 publications

(4 citation statements)

References 20 publications

(39 reference statements)

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“…Although a variety of control techniques exist, (e.g. both feedback and feedforward [9] control are used within GEO 600), we consider only the most commonly used control type at GEO 600, linear inverting feedback. This works by measuring the deviation of a parameter of a given system (the plant) from a desired operating point.…”

Section: Example Applicationsmentioning

confidence: 99%

“…• in phase (for a calculation of this, see [9]). Thus, to make time-domain noise subtraction practical, either verified long-term stability of the noise coupling or real-time adaptive monitoring are needed.…”

Section: Technical-noise Subtractionmentioning

confidence: 99%

“…The noise reduction possible with this system depends on the accuracy with which the filter represents the actual noise coupling. A factor of ten reduction requires that the filter be roughly within about 10% in amplitude and 5 • in phase (for a calculation of this, see [9]). Thus, to make time-domain noise subtraction practical, either verified long-term stability of the noise coupling or real-time adaptive monitoring are needed.…”

Section: Technical-noise Subtractionmentioning

confidence: 99%

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Linear projection of technical noise for interferometric gravitational-wave detectors

Smith¹,

Ajith²,

Grote³

et al. 2005

Class. Quantum Grav.

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An international network of interferometric gravitational-wave detectors is now in operation, and has entered a period of intense commissioning focused on bringing the instruments to their theoretical sensitivity limits. To expedite this process, noise analysis techniques have been developed by the groups associated with each instrument. We present methods of noise analysis that were developed and utilized for the commissioning of the GEO 600 detector. The focal point of this paper is a technique called noise projection that is used to determine the levels of contribution of various noise sources to the detector output. Example applications of this method to control loops typical of those employed in an interferometric GW detector are presented. Possible extensions of noise projections, including technical noise subtraction and gravitationalwave vetoes are also discussed.

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Section: Example Applicationsmentioning

confidence: 99%

Section: Technical-noise Subtractionmentioning

confidence: 99%

Section: Technical-noise Subtractionmentioning

confidence: 99%

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Linear projection of technical noise for interferometric gravitational-wave detectors

Smith¹,

Ajith²,

Grote³

et al. 2005

Class. Quantum Grav.

Self Cite

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“…Similar to other GW detectors, the sensitivity of the instrument is affected both by fundamental noise sources arising from thermal, seismic or quantum mechanical properties of light and by technical ones arising from the various auxiliary control loops that are used to keep it in a stable operating point. The common strategy adopted, principally for seismic and technical noise sources, is to estimate the linear part of the coupling and subtract it off via online feedforward cancellation [10][11][12][13]. Since the strain and auxiliary channel data is saved to disk, it is also possible to perform offline subtraction at a later time.…”

Section: Introductionmentioning

confidence: 99%

Bilinear noise subtraction at the GEO 600 observatory

Mukund,

Lough,

Affeldt

et al. 2020

Preprint

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We develop a scheme to subtract off bilinear noise from the gravitational wave strain data and demonstrate it at the GEO 600 observatory. Modulations caused by test mass misalignments on longitudinal control signals are observed to have a broadband effect on the mid-frequency detector sensitivity ranging from 50 Hz to 500 Hz. We estimate this bilinear coupling by making use of narrowband signal injections that are already in place for noise projection purposes. A coherent bilinear signal is constructed by a two-stage system identification process where the involved couplings are approximated in terms of stable rational functions. The time-domain filtering efficiency is observed to depend upon the system identification process especially when the involved transfer functions cover a large dynamic range and have multiple resonant features. We improve upon the existing filter design techniques by employing a Bayesian adaptive directed search strategy that optimizes across the several key parameters that affect the accuracy of the estimated model. The resulting post-offline subtraction leads to a suppression of modulation side-bands around the calibration lines along with a broadband reduction of the mid-frequency noise floor. The filter coefficients are updated periodically to account for any non-stationarities that can arise within the coupling. The observed increase in the astrophysical range and a reduction in the occurrence of non-astrophysical transients suggest that the above method is a viable data cleaning technique for current and future gravitational wave observatories.

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